A panel of "first generation" monoclonal antibodies (MAbs) has been developed which are directed to several distinct domains of the HTLV-1 surface protein. In addition, a sensitive chemiluminescent immunoassay has been constructed for the detection of HTLV-1 surface protein. Using monoclonal antibody affinity chromatography, gp46 will be purified from viral lysates and used as immunogen in order to develop a "second generation" panel of MAbs to native viral surface protein. Anti-gp46 MAbs will be studied for their capacity to neutralize the infectivity of HTLV- 1. The effects of MAbs on viral adsorption, cell-free transmission, and cell-to-cell infection will be investigated. The precise gp46 epitopes which react with neutralizing MAbs will be determined using peptide scanning techniques and mimetope peptides. The resulting data will support long term studies in the areas of receptor analysis, viral pathogenesis, and in the design of anti-viral modalities.